In the field of medicine, medical image diagnostic apparatuses configured to image the inside of a subject with use of radiation such as X-rays, ultrasound waves, nuclear magnetic resonance, or other methods have hitherto been used. For example, a medical image diagnostic apparatus provides a doctor with a medical image in which the inside of a subject is photographed. The doctor views the provided medical image to observe the conditions of the inside of the subject, thereby making a diagnosis.
Image diagnosis using medical images involves setting a region of interest (ROI) on a medical image and making a diagnosis based on an index value in the set region of interest. For example, elastography using an ultrasound diagnostic apparatus involves imaging the stiffness of living tissue and making a diagnosis with use of various index values measured from an ROI within the image. Specifically, mammary tumor diagnosis involves making a diagnosis by using the ratio of the stiffness of a tumor part to the stiffness of a peripheral region as an index. Liver fibrosis diagnosis involves determining the degree of fibrosis by classifying liver fibrosis into several fibrosis stages depending on the stiffness.
Such a diagnosis based on an index value in a region of interest is not limited to the above-mentioned examples, and there are various diagnostic methods. Even when the same index value is used as in the above-mentioned examples, diagnostic standards vary from one diagnosis to another and cannot be determined uniquely. It is therefore not easy to make a diagnosis based on an index value in a region of interest.